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Generally, any color "screen of death" on reboot (whether it rebooted spontaneously or you deliberately powered down/back up) is a pretty big sign of something going wrong in hardware. If it's only happened once, you're not stock in a bootloop, and you're not jailbroken, it may be nothing to worry about. (If you're jailbroken, there's a chance conflicting tweaks are triggering this behavior, so start by removing the most recent ones.)

But if it's happened multiple times or you're stuck in a bootloop, take it to Apple for exchange.
 
It will keep rebooting sometimes for half hour.Its not jail broken about 3 months old.
 
It will keep rebooting sometimes for half hour.Its not jail broken about 3 months old.

Take it in, it's defective. Get your data off of it ASAP, and get it exchanged.

I had to exchange mine a few weeks ago for blue screen of death reboots, so I know what a nuisance this problem is. My replacement iphone 6 is so much better in so many little ways that I didn't realize were related to the rebooting issue. I'm only sorry i waited so long to exchange. Hopefully your experience will be similar!
 
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